Integral-type liquid crystal panel with image sensor function

ABSTRACT

A display device using a novel semiconductor device, which includes a pixel matrix, an image sensor, and a peripheral circuit for driving those, that is, which has both a camera function and a display function, and is made intelligent, is provided and a method of manufacturing the same is also provided. One pixel includes a semiconductor device for display and a semiconductor for light reception, that is, one pixel includes semiconductor devices (insulated gate-type field effect semiconductor device) for controlling both display and light reception, so that the display device having a picture reading function is made miniaturized and compact.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device having an image sensorfunction and a display function, and particularly to an electronicequipment, such as an active matrix panel with a display portion made ofa pixel portion including a plurality of pixel electrodes disposed inmatrix, a portable terminal unit with such a display portion, or apersonal computer with such a display portion, and also to a method ofmanufacturing the same.

2. Description of the Related Art

In recent years, a technique of a TFT using polycrystal silicon called apolysilicon TFT has been diligently investigated. As a result, itbecomes possible to manufacture a driving circuit, such as a shiftregister, with polysilicon TFTs, and further, an active matrix typeliquid crystal panel in which a pixel portion and a peripheral drivingcircuit for driving the pixel portion are integrated on the samesubstrate, has been put to practical use. Thus, the cost of the liquidcrystal panel is lowered, the size thereof is reduced, the weightthereof is decreased, and the liquid crystal panel is used as a displayportion of various information equipments or portable equipments, suchas a personal computer, a portable telephone, a video camera, and adigital camera.

Recently, a pocket-sized small portable information processing terminalunit, which is superior in portability to a note-sized personal computerand is inexpensive, has been put to practical use, and an active matrixtype liquid crystal panel is used for its display portion. In such andinformation processing terminal, although data can be inputted from thedisplay portion by a touch-pen system, it is necessary to connect theterminal with a peripheral device for reading an image, such as ascanner or a digital camera, in order to input character/drawinginformation on a paper or picture information. For this reason, theportability of the information processing terminal is hindered. Also, aneconomical load for purchasing a peripheral device is imposed on a user.

An active matrix type display device is used also for a display portionof a TV meeting system, a TV telephone, a terminal for the internet, andthe like. Although such a system or terminal is provided with a camera(CCD camera) for photographing an image of a dialogist or a user, adisplay portion and a reading portion (sensor portion) are separatelymanufactured and are modularized. Thus, the manufacturing cost becomeshigh.

SUMMARY OF THE INVENTION

An object of the present invention is to overcome the foregoingproblems, and to provide a display device using a novel semiconductordevice which includes a pixel matrix, an image sensor, and a peripheralcircuit for driving those, that is, includes both a camera function anda display function and is made intelligent.

Another object of the present invention is to inexpensively manufacturea display device using a novel semiconductor device which is madeintelligent by causing an image sensor to coordinate with a pixel matrixand a peripheral driving circuit in the structure and manufacturingprocess.

In order to achieve the above objects, in the present invention, such astructure is adopted that a semiconductor device for display and asemiconductor device for light reception are disposed on the samesubstrate. A liquid crystal display portion including a pixel electrodeand a semiconductor device for display, and a sensor portion including asemiconductor device for light reception are not separately disposed,but a novel device structure which includes the semiconductor device fordisplay and the semiconductor device for light reception in one pixel,that is, as shown in FIGS. 1 and 2, a structure which includessemiconductor devices (insulated gate field effect semiconductor device)for carrying out control of both display and light reception in onepixel, is adopted, so that a display device with a picture readingfunction is made small and compact.

According to a first aspect of the present invention, an integral-typeliquid crystal display panel with an image sensor function comprises adisplay portion made of a pixel matrix including at least pixelelectrodes in matrix and a first semiconductor device connected to eachof the pixel electrodes, and a sensor portion including at least aphotoelectric conversion element and a second semiconductor deviceconnected to the photoelectric conversion element, wherein the sensorportion is disposed on the same substrate as the display portion, andlight from a back surface of the substrate is received by the sensorportion.

According to a second aspect of the present invention, an integral-typeliquid crystal display panel with an image sensor function comprises adisplay portion made of a pixel matrix including at least pixelelectrodes in matrix and a first semiconductor device connected to eachof the pixel electrodes, and a sensor portion including at least aphotoelectric conversion element and a second semiconductor deviceconnected to the photoelectric conversion element, wherein the sensorportion is disposed on the same substrate as the display portion, thedisplay portion and the sensor portion have the same pixel size, andlight from a back surface of the substrate is received by the sensorportion.

According to a third aspect of the present invention, an integral-typeliquid crystal display panel with an image sensor function comprises adisplay portion made of a pixel matrix including at least pixelelectrodes in matrix and a first semiconductor device connected to eachof the pixel electrodes, and a sensor portion including a photoelectricconversion element and a second semiconductor device connected to thephotoelectric conversion element, wherein the sensor portion is disposedon the same substrate as the display portion, the first semiconductordevice and the second semiconductor device are disposed in the samematrix, and the pixel electrode connected to the first semiconductordevice exists over the second semiconductor device.

According to a fourth aspect of the present invention, an integral-typeliquid crystal display panel with an image sensor function comprises adisplay portion made of a pixel matrix including at least pixelelectrodes in matrix and a first semiconductor device connected to eachof the pixel electrodes, and a sensor portion including a photoelectricconversion element and a second semiconductor device connected to thephotoelectric conversion element, wherein the sensor portion is disposedon the same substrate as the display portion; the photoelectricconversion element includes at least an upper electrode, a photoelectricconversion layer, and a lower electrode, the upper electrode is made ofa metal having reflectivity to at least visible light, and the lowerelectrode is made of a transparent conductive film.

According to a fifth aspect of the present invention, a method ofmanufacturing an integral-type liquid crystal display panel with animage sensor function which comprises a pixel matrix including pixelelectrodes disposed in matrix and a first semiconductor device connectedto each of the pixel electrodes, and an image sensor with a lightreceiving portion including a photoelectric conversion element and asecond semiconductor device connected to the photoelectric conversionelement, which are disposed on the same substrate as the pixel matrix,the method comprising: a first step of forming the first semiconductordevice and the second semiconductor device on the substrate; a secondstep of forming a lower electrode connected to the second semiconductordevice and made of a transparent conductive film; a third step offorming a photoelectric conversion layer on the lower electrode; and afourth step of forming an upper electrode contacting on thephotoelectric conversion layer.

According to a sixth aspect of the present invention, a method ofmanufacturing an integral-type liquid crystal display panel with animage sensor function which comprises a pixel matrix including pixelelectrodes disposed in matrix and a first semiconductor device connectedto each of the pixel electrodes, and an image sensor with a lightreceiving portion including a photoelectric conversion element and asecond semiconductor device connected to the photoelectric conversionelement, which are disposed on the same substrate as the pixel matrix,the method comprising: a first step of forming the first semiconductordevice and the second semiconductor device on the substrate; a secondstep of forming a first insulating film covering at least the firstsemiconductor device and the second semiconductor device; a third stepof forming a transparent conductive film on the first insulating film; afourth step of forming a lower electrode connected to the secondsemiconductor device by patterning the transparent conductive film; afifth step of forming a photoelectric conversion layer on the lowerelectrode; and a sixth step of forming an upper electrode contacting onthe photoelectric conversion layer.

According to a seventh aspect of the present invention, an integral-typeliquid crystal panel with an image sensor function comprises aphotoelectric conversion element including a lower electrode, aphotoelectric conversion layer formed on the lower electrode, and anupper electrode formed on the photoelectric conversion layer; and asensor portion including at least one active element connected to thephotoelectric conversion element, the sensor portion being disposed onan insulating substrate, wherein the upper electrode is made of a metalhaving reflectivity to at least visible light, and the lower electrodeis made of a conductive film having transparency to at least visiblelight.

According to an eighth aspect of the present invention, an integral-typeliquid crystal display panel with an image sensor function comprises adisplay portion made of a pixel matrix including at least pixelelectrodes in matrix and an active element connected to each of thepixel electrodes, and a sensor portion including at least aphotoelectric conversion element and an active element group connectedto the photoelectric conversion element, wherein the sensor portion isdisposed on the same substrate as the display portion, and light from aback surface of the substrate is received by the sensor portion.

According to a ninth aspect of the present invention, an integral-typeliquid crystal display panel with an image sensor function comprises adisplay portion made of a pixel matrix including at least pixelelectrodes in matrix and an active element connected to each of thepixel electrodes, and a sensor portion including at least aphotoelectric conversion element and an active element group connectedto the photoelectric conversion element, wherein the sensor portion isdisposed on the same substrate as the display portion, the displayportion and the sensor portion have the same pixel size, and light froma back surface of the substrate is received by the sensor portion.

According to a tenth aspect of the present invention, an integral-typeliquid crystal display panel with an image sensor function comprises adisplay portion made of a pixel matrix including at least pixelelectrodes in matrix and an active element connected to each of thepixel electrodes, and a sensor portion including at least aphotoelectric conversion element and an active element group connectedto the photoelectric conversion element, wherein the sensor portion isdisposed on the same substrate as the display portion, the activeelement and the active element group are disposed in the same matrix,and the pixel electrode connected to the active element exists over theactive element group.

According to an eleventh aspect of the present invention, anintegral-type liquid crystal display panel with an image sensor functioncomprises a display portion made of a pixel matrix including at leastpixel electrodes in matrix and an active element connected to each ofthe pixel electrodes, and a sensor portion including at least aphotoelectric conversion element and an active element group connectedto the photoelectric conversion element, wherein the sensor portion isdisposed on the same substrate as the display portion, the photoelectricconversion element includes at least an upper electrode, a photoelectricconversion layer, and a lower electrode, the upper electrode is made ofa metal having reflectivity to at least visible light, and the lowerelectrode is made of a transparent conductive film.

In the eighth to eleventh aspects of the present invention, the activeelement group includes at least an amplification transistor, a resettransistor, and a selection transistor.

According to a twelfth aspect of the present invention, a method ofmanufacturing an integral-type liquid crystal display panel with animage sensor function which comprises a pixel matrix including pixelelectrodes disposed in matrix and an active element connected to each ofthe pixel electrodes, and an image sensor with a light receiving portionincluding a photoelectric conversion element and an active element groupconnected to the photoelectric conversion element, which are disposed onthe same substrate as the pixel matrix, the method comprising: a firststep of forming the active element and the active element group on thesubstrate; a second step of forming a lower electrode connected to theactive element group and made of a transparent conductive film; a thirdstep of forming a photoelectric conversion layer on the lower electrode;and a fourth step of forming an upper electrode on the photoelectricconversion layer.

According to a thirteenth aspect of the present invention, a method ofmanufacturing an integral-type liquid crystal display panel with animage sensor function which comprises a pixel matrix including pixelelectrodes disposed in matrix and an active element connected to each ofthe pixel electrodes, and an image sensor including a photoelectricconversion element and an active element group connected to thephotoelectric conversion element, which are disposed on the samesubstrate as the pixel matrix, the method comprising: a first step offorming the active element and the active element group on thesubstrate; a second step of forming a first insulating film covering atleast the active element and the active element group; a third step offorming a transparent conductive film on the first insulating film; afourth step of forming a lower electrode connected to the active elementgroup by patterning the transparent conductive film; a fifth step offorming a photoelectric conversion layer on the lower electrode; and asixth step of forming an upper electrode contacting on the photoelectricconversion layer.

In the twelfth aspect or thirteenth aspect of the present invention, theactive element group includes at least an amplification transistor, areset transistor, and a selection transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a sectional view of a pixel of the present invention;

FIGS. 2A and 2B are views showing an example of front surfacearrangement and back surface arrangement of one pixel;

FIG. 3 is a circuit diagram of the present invention.

FIGS. 4A and 4B are views of the entire of a liquid crystal panel;

FIGS. 5A to 5D are views showing steps of forming a sensor portion and adisplay element on one pixel;

FIGS. 6A to 6C are views showing steps of forming a sensor portion and adisplay element on one pixel;

FIG. 7 is a sectional view of a pixel of a second embodiment;

FIGS. 8A to 8D are views of manufacturing steps of the secondembodiment;

FIGS. 9A to 9C are views of manufacturing steps of the secondembodiment;

FIG. 10 is a circuit diagram of a third embodiment; and

FIGS. 11A to 11D show an applied examples of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First, a typical mode using the present invention will be describedbelow. In the present invention, as shown in FIG. 1, such a novelelement structure is adopted that one pixel includes one semiconductordevice (TFT) for display and at least one semiconductor device (TFT) forlight reception. A device is constructed such that a potential isapplied to a liquid crystal oriented by an oriented film formed on areflective electrode of this element so that display is made on a liquidcrystal display surface, and a sensor portion reads a light signalincident on the back surface of the liquid crystal display surface sothat a picture is taken in. The panel structure of this invention isshown in FIGS. 4A and 4 b. FIG. 3 is a view showing a circuit diagram ofthe panel of the present invention simply.

As shown in FIG. 4A, a liquid crystal panel has such a panel arrangementthat a sensor driving circuit 403 for driving a sensor portion and adisplay driving circuit 404 for driving a display portion are providedaround a display portion and sensor portion 402.

In the present invention, such a system is adopted that the sensorportion reads light signal data incident on the back surface of a liquidcrystal display surface, stores the data in an external storage deviceor the like connected to a sensor terminal portion 406, the data areprocessed for picture display, and then, the data are inputted from adisplay lead terminal portion 405, so that a picture is displayed ontothe display portion 402. Such a structure may be adopted that a memorycircuit or the like is formed on the same substrate, so that thesesystems are carried out on the same substrate. Moving pictures or stillpictures taken in by the sensor portion are displayed on the liquidcrystal panel almost in realtime. Moreover, such a structure may beadopted that data from the outside of the device can be displayed on thedisplay portion.

FIG. 4B is a simplified view of a sectional structure taken along lineA-B in FIG. 4A. An element substrate 400 is bonded to an oppositesubstrate 401 through a seal material 407, and a liquid crystal material410 is held between the substrates. A picture is provided to a user byusing light incident on the liquid crystal display surface.

In the present invention, the sensor portion senses a light signalhaving passed through an optical system 409 attached to the backsurface, a color filter 411, and further the substrate 400. Thus, it ispreferable to use the substrate 400 having extremely excellenttransparency to visible light.

FIG. 1 is a sectional view of one pixel making up the display portionand sensor portion 402 in FIG. 4, and FIGS. 2A and 2B are views showingan example of an arrangement using such an element.

FIG. 2A indicates a surface top view and a sectional view taken alongA-B corresponds to FIG. 1. In FIG. 2A, the sensor portion is coveredwith a reflective electrode 121. In FIG. 2A, such a structure is adoptedthat the reflective electrode 121 is not formed on wiring lines 106,107, 115 and 116. The liquid crystal display is made by using thisreflective electrode 121. Wiring lines concerned in the liquid crystaldisplay are the pixel portion TFT signal line 115 and the pixel portionTFT gate line 106.

FIG. 2B shows the back surface of FIG. 2A. Actually, since protectiveshading (light shielding) films 104 and 105 for a TFT are formed,although a TFT portion can not be observed, for convenience, onlyforming portions of the shading films 104 and 105 are shown in thedrawing. In addition, although a photoelectric conversion layer 118 maylo be formed on the wiring lines 106, 107, 115, and 116 and a pixel TFT,FIG. 2B shows a structure in which the photoelectric conversion layer118 is not formed. A light signal incident on the photoelectricconversion layer is read, and data are transmitted to the sensor portionTFT signal line 116. Here, wiring lines concerned in picture reading arethe sensor portion TFT signal line 116 and the sensor portion TFT gateline 107.

That is, as shown in FIG. 1 or FIGS. 2A and 2B, since the presentinvention is constructed such that one pixel includes two TFTs, thepitch of pixels and the number of bits become the same between the lightreceiving matrix and the display matrix. The shading film 104 isprovided on the substrate 100 at a display element side, so that such astructure is adopted that the TFT is protected against light incidentfrom the back surface. Moreover, such a structure may be adopted thatthe shading film 105 may be provided on the TFT at a sensor elementside. Moreover, such a structure may be adopted that the shading filmmay be directly provided on the back surface of the substrate.

After an under film 101 is formed on the shading films 104 and 105, aplurality of TFTs for displaying or reading pictures are formed. Theback surface of the substrate here indicates a substrate surface onwhich a TFT is not formed. The structure of the TFT may be a top gatetype or a bottom gate type.

Then a transparent conductive film 117 connected to a drain electrode112 of the TFT at the sensor element side is provided. This conductivefilm is a film forming a lower electrode of a photoelectric conversionelement, and is formed on a pixel region other than the upper portion ofthe TFT of the display element. A photoelectric conversion layer isprovided on the conductive film, and an upper electrode 119 is furtherprovided thereon, so that a photoelectric conversion element iscompleted.

On the other hand, with respect to the TFT at the display element side,a pixel reflective electrode 121 connected to a drain wiring line 114 isprovided. Such a structure may be adopted that the pixel reflectiveelectrode covers the sensor portion and a wiring line. In the case wherethe structure of covering the wiring line is adopted, capacitance isformed with a dielectric of an insulating film existing between thewiring line and the pixel reflective electrode. Since the presentinvention relates to a reflection type display, a metal material havingreflectivity is used as the pixel electrode.

A manufacturing process of the present invention is substantially thesame as manufacturing steps of a conventional display device exceptmanufacturing steps of a photoelectric conversion element. Thus, since aconventional manufacturing process can be used, the device can bemanufactured easily and at low cost. Moreover, even if a sensor functionis included, the shape and size of the device manufactured through thepresent invention are not changed from a conventional panel. Thus, itssize can be made small and its weight can be made light.

Although the present invention will be described below in more detailwith respect to the preferred embodiments, it is needless to say thatthe present invention is not limited to these embodiments.

Embodiment 1

In this embodiment, an example of manufacturing steps of a liquidcrystal panel having a sensor portion receiving light from a backsurface of a liquid crystal display surface will be described in detailwith reference to FIGS. 5A to 5D and FIGS. 6A to 6C.

First, an under film 101 is formed on the entire surface of atransparent substrate 100. As the transparent substrate 100, a glasssubstrate or a quartz substrate having transparency may be used. As theunder film, a silicon oxide film with a thickness of 150 nm was formedby a plasma CVD method. In this embodiment, prior to this step offorming the under film, there were provided a shading film 104 forprotecting a display pixel portion TFT against light from the backsurface, and a shading film 104 for protecting a light receiving sensorportion TFT against light from the back surface. In this embodiment,although the shading films are provided to prevent noise anddeterioration, it is not particularly necessary to provide them if anopening rate is prioritized.

Next, an amorphous silicon film with a thickness of 30 to 100 nm,preferably 30 nm was formed by a plasma CVD method, and a polycrystalsilicon film was formed by irradiation of excimer laser light. As themethod of crystallizing the amorphous silicon film, a thermalcrystallizing method called an SPC, an RTA method using irradiation ofinfrared rays, a method of using thermal crystallization and laserannealing, and the like may be used.

Next, the polycrystal silicon film is patterned to form island-likesemiconductor layer 102 for making source regions, drain regions,channel formation regions of TFTs 200 and 300. Then a gate insulatingfilm 103 covering these semiconductor layers is formed. The gateinsulating film with a thickness of 100 nm is formed by a plasma CVDmethod using silane (SiH₄) and N₂O as a raw material gas (FIG. 5A).

Next, a conductive film is formed. Here, although aluminum was used as aconductive film material, a film mainly containing titanium, silicon, ora lamination film of those films may be used. In this embodiment, thealuminum film with a thickness of 200 to 500 nm, typically 300 nm isformed by a sputtering method. For the purpose of suppressing generationof hillocks or whiskers, scandium (Sc), titanium (Ti), or yttrium (Y) of0.04 to 1.0 wt % is made to be contained in the aluminum film.

Next, a resist mask is formed, and the aluminum film is patterned toform an electrode pattern, so that a pixel gate electrode 106 and asensor portion gate electrode 107 are formed.

Next, an offset structure is formed by a well-known method. Further, anLDD structure may be formed by a well-known method (FIG. 5B).

Then a first interlayer insulating film 113 is formed, and contact holesreaching N-type high concentration impurity regions (source region,drain region) are formed. Thereafter, a metal film is formed and ispatterned to form wiring lines 112, 114, 115, and 116.

In this embodiment, the first interlayer insulating film 113 is formedof a silicon nitride film with a thickness of 500 nm. As the firstinterlayer insulating film, a silicon oxide film or a silicon nitrideoxide film may be used other than the silicon nitride film. Moreover, amultilayer film of these insulating films may be used.

As the metal film of a starting film of the wiring lines, in thisembodiment, a lamination film made of a titanium film, an aluminum film,and a titanium film is formed by a sputtering method. The thicknesses ofthese films are 100 nm, 300 nm, and 100 nm, respectively.

Through the foregoing process, the pixel TFT 200 and the light receivingportion TFT 300 are completed at the same time (FIG. 5C).

Next, a transparent conductive film being in contact with the drainwiring line 112 of the light receiving portion TFT is formed on thefirst interlayer insulating film 113. The transparent conductive film isformed and is patterned, so that a transparent electrode 117 of aphotoelectric conversion element is formed. ITO or SnO₂ may be used forthe transparent conductive film 117. In this embodiment, an ITO filmwith a thickness of 100 nm is formed as the transparent conductive film.

While an upper electrode is formed of a transparent conductive film in ageneral active type image sensor, the image sensor of this embodiment isdifferent from the general image sensor in that a lower electrode isformed of the transparent conductive film. In this invention, sincelight is received from the back surface, the lower electrode is formedof the transparent conductive film (FIG. 5D).

Next, an amorphous silicon film 118 containing hydrogen (hereinafterreferred to as a-Si:H film) functioning as a photoelectric conversionlayer is formed on the entire surface of the substrate. Then patterningis carried out so that the a-Si:H film remains at only a light receivingportion to form the photoelectric conversion layer.

Next, a conductive film is formed on the entire surface of thesubstrate. In this embodiment, a titanium film with a thickness of 200nm is formed as the conductive film by a sputtering method. Thisconductive film is patterned to form an upper electrode 119 connected tothe light receiving portion TFT. Titanium or chromium may be used as theconductive film (FIG. 6A).

A light receiving effective portion of this sensor portion is a portionin one pixel, which is surrounded by the gate wiring lines 106 and 107and the signal wiring lines 115 and 116 and in which the shading films104 and 105 are not formed. The sizes of pixels in this lo embodimentare the same between the display portion and the sensor portion, and thesize is made 60×60 μm. However, the size is not particularly limited aslong as it is within the range of 16×16 μm to 70×70 μm.

Then a second interlayer insulating film 120 is formed. When a resinfilm of polyimide, polyamide, polyimide amide, acryl, or the like isformed as an insulating film for forming the second interlayerinsulating film, a flat surface can be obtained, so that such a resinfilm is preferable. Alternatively, a lamination layer structure may beadopted such that an upper layer of the second interlayer insulatingfilm is the foregoing resin film, and a lower layer thereof is a singlelayer or multilayer film of inorganic insulating materials such assilicon oxide, silicon nitride, and silicon initride oxide. In thisembodiment, a polyimide film with a thickness of 0.7 μm was formed asthe insulating film on the entire surface of the substrate (FIG. 6B).

Further, a contact hole reaching the drain wiring line 114 is formed inthe second interlayer insulating film. A conductive film is again formedon the entire surface of the substrate, and is patterned to form a pixelelectrode 121 connected to the pixel TFT. In this embodiment, a titaniumfilm with a thickness of 200 nm is formed as the conductive film by asputtering method. Titanium, chromium, or aluminum may be used for theconductive film.

Through the foregoing steps, an element substrate as shown in FIG. 6C orFIG. 1 is completed.

Then this element substrate and an opposite substrate are bonded to eachother through a seal material, and a liquid crystal is enclosed so thata reflection type liquid crystal panel is completed. The liquid crystalcan be freely selected according to an operation mode (ECB mode,guest-host mode) of the liquid crystal. The opposite substrate isconstructed such that a transparent conductive film and an oriented filmare formed on a transparent substrate. Other than those, a black mask ora color filter may be provided as the need arises.

Subsequently, as shown in FIG. 4B, a color filter 411, an optical system409, and a support 408 for fixing the optical system 409 are provided onthe back surface of the liquid crystal panel, and the device ismanufactured.

In this way, the liquid crystal panel having the sensor portion whichreceives light from the back surface of the liquid crystal displaysurface is completed. FIG. 3 is a circuit diagram of this embodimentsimplified into 2×2 pixels for convenience.

The most remarkable feature in this circuit diagram is that the liquidcrystal display element and the sensor element are independent of eachother.

The liquid crystal display element is mainly made up of a liquid crystalmaterial 302, a capacitance 314, a pixel TFT 303, a gate line connectedto a display gate driver 311, a display signal driver 310, a displayinput signal line 306, and a fixed potential line 304.

The sensor element is mainly made of a photodiode PD 301, a sensor TFT312, an output signal line of a sensor, a sensor horizontal shiftregister 308, a sensor vertical shift register 309, and a fixedpotential line 305.

Embodiment 2

In this embodiment, an example of manufacturing steps of a liquidcrystal panel including a sensor portion receiving light from a backsurface of a liquid crystal display surface will be described in detailwith reference to FIGS. 8A to 8D and FIGS. 9A to 9C.

The feature of this embodiment is that one pixel includes a displaypixel portion TFT and a light receiving sensor portion TFT, aninterlayer insulating film covering these TFTs are formed, aphotoelectric conversion layer is formed on the interlayer insulatingfilm, and is connected to the light receiving sensor portion TFT. Thus,as compared with the embodiment 1, the opening rate is large.

First, an under film 701 is formed on the entire surface of atransparent substrate. A glass substrate or a quartz substrate may beused as a transparent substrate 700. A silicon oxide film with athickness of 200 nm was formed as the under film by a plasma CVD method.In this embodiment, prior to the step of forming the under film, ashading film 704 for protecting the display pixel TFT portion againstlight from the back surface, and a shading film 706 for protecting thelight receiving sensor TFT portion against light from the back surfacewere provided.

Next, an amorphous silicon film with a thickness of 30 to 100 nm,preferably, 30 nm was formed by a plasma CVD method, and a polycrystalsilicon film is formed by irradiation of excimer laser light. As themethod of crystallizing the amorphous silicon film, a thermalcrystallizing method called an SPC, an RTA method using irradiation ofinfrared rays, a method of using thermal crystallization and laserannealing, and the like may be used.

Next, the polycrystal silicon film is patterned to form island-likesemiconductor layers 702 for making source regions, drain regions, andchannel formation regions of TFTs 800 and 900. Next, a gate insulatingfilm 703 covering these semiconductor layers is formed. The gateinsulating film with a thickness of 120 nm is formed by a plasma CVDmethod using silane (SiH₄) and N₂O as a raw material gas (FIG. 8A).

Next, a conductive film is formed. Here, although aluminum was used as aconductive film material, a film mainly containing titanium, silicon, ora lamination film of those films may be used. In this embodiment, thealuminum film with a thickness of 300 to 500 nm, typically 300 nm isformed by a sputtering method. For the purpose of suppressing thegeneration of hillocks or whiskers, scandium (Sc), titanium (Ti), oryttrium (Y) of 0.04 to 1.0 wt % is made to be contained in the aluminumfilm.

Next, a resist mask is formed, and the aluminum film is patterned toform an electrode pattern, so that gate electrodes 705 and 707 areformed.

Next, LDD structures 709 and 710 are formed by a well-known method.Besides, an offset structure may be formed by a well-known method.Reference numerals 708 and 711 denote high concentration impurityregions, and 712 denotes a channel region (FIG. 8B).

Then a first interlayer insulating film 713 is formed, and contact holesreaching N-type high concentration impurity regions (source region,drain region) are formed. Thereafter, a metal film is formed and ispatterned to form wiring lines 714, 715, 722, and 723.

In this embodiment, the first interlayer insulating film is formed of asilicon nitride film with a thickness of 500 nm. As the first interlayerinsulating film, a silicon oxide film or a silicon nitride film may beused other than the silicon nitride oxide film. Moreover, a multilayerfilm of these insulating films may be used.

As the metal film of a starting film of the wiring electrodes 714, 715,722, and 723, in this embodiment, a lamination film made of a titaniumfilm, an aluminum film, and a titanium film is formed by a sputteringmethod. The thicknesses of these films are 100 nm, 300 nm, and 100 nm,respectively.

Through the foregoing process, the pixel TFT 800 and the light receivingportion TFT 900 are completed at the same time (FIG. 8C).

Next, a second interlayer insulating film 716 covering the TFTs isformed. The main point different from the embodiment 1 is that thissecond interlayer insulating film is provided so that a photoelectricconversion layer formed in a subsequent step can be widely formed. Bydoing so, a light receiving area (opening rate) of a sensor can be madewider than the embodiment 1. A resin film which cancels asperities of alower layer so that a flat surface can be obtained, is preferable as thesecond interlayer insulating film. As such a resin film, polyimide,polyamide, polyimide amide, or acryl may be used. Alternatively, anupper layer of the second interlayer insulating film may be theforegoing resin film for the purpose of obtaining the flat surface, anda lower layer thereof may be a single layer or a multilayer of inorganicinsulating material such as silicon oxide, silicon nitride, and siliconnitride oxide. In this embodiment, a polyimide film with a thickness of1.5 μm is formed as the second interlayer insulating film.

Next, after a contact hole reaching the wiring line 723 of the lightreceiving portion TFT 900 is formed in the second interlayer insulatingfilm 716, a transparent conductive film is formed. As the transparentconductive film, ITO or SnO₂ may be used. In this embodiment, an ITOfilm with a thickness of 120 nm is formed.

Next, the transparent conductive film is patterned to form a lowerelectrode 717 connected to the light receiving portion TFT 900 (FIG.8D).

Next, an amorphous silicon film 718 containing hydrogen (hereinafterreferred to as a-Si:H film) functioning as a photoelectric conversionlayer is formed on the entire surface of the substrate. Then patterningis carried out so that the a-Si:H film remains at only a light receivingportion to form the photoelectric conversion layer.

Next, a conductive film is formed on the entire surface of thesubstrate. In this embodiment, a titanium film with a thickness of 200nm is formed as the conductive film by a sputtering method. Thisconductive film is patterned to form an upper electrode 719 connected tothe light receiving portion TFT. Titanium or chromium may be used forthe conductive film.

While an upper electrode in a general active type image sensor is formedof a transparent electrode, the image sensor of this embodiment isdifferent from the general image sensor in that a lower electrodethereof is formed of a transparent electrode. In this invention, sincelight is received from the back surface, the lower electrode is formedof a transparent conductive film (FIG. 9A).

Then a third interlayer insulating film 720 is formed. If a resin filmof polyimide, polyamide, polyimide amide, or acryl is used as aninsulating film forming the third interlayer insulating film, a flatsurface can be obtained, so that such a resin film is preferable.Alternatively, an upper layer of the third interlayer insulating filmmay be the foregoing resin film and a lower layer thereof may be asingle layer or multilayer film of inorganic insulating material such assilicon oxide, silicon nitride, and silicon nitride oxide. In thisembodiment, a polyimide film with a thickness of 0.5 μm was formed onthe entire surface of the substrate (FIG. 9B).

The maximum process temperature of the present invention after theformation of the polyimide film is made a temperature lower than theheat resistance temperature 320° C. of this polyimide.

Further, a contact hole reaching the wiring line is formed in the thirdand second interlayer insulating films. A conductive film is againformed on the entire surface of the substrate, and is patterned to forma pixel electrode 721 connected to the pixel TFT. In this embodiment, atitanium film with a thickness of 200 nm is formed as the conductivefilm by a sputtering method. Titanium or chromium may be used for theconductive film.

Through the foregoing steps, an element substrate as shown in FIG. 9C orFIG. 7 is completed.

Thereafter, similarly to the embodiment 1, the element substrate and anopposite substrate are bonded to each other through a seal material, anda liquid crystal is enclosed to complete a reflection type liquidcrystal panel. A color filter 411, an optical system 409, and a support408 for fixing the optical system 409 are provided on the back surfaceof the liquid crystal panel, and the device is manufactured.

In this way, the liquid crystal panel including the sensor portionreceiving light from the back surface of the liquid crystal displaysurface is completed.

Embodiment 3

Although examples in which a non-amplifying image sensor is used, areshown in the embodiments 1 and 2, this embodiment relates to anamplifying type image sensor. More specifically, an example in which animage sensor including semiconductor devices disposed in matrix, will bedescribed.

FIG. 10 is a simplified view of a circuit diagram of a liquid crystalpanel using this amplifying type image sensor. The amplifying type imagesensor uses three TFTs of a reset transistor T₁, an amplificationtransistor T₂, and a selection transistor T₃. The most remarkablefeature in this circuit diagram is that this diagram includes a resetline 1012, a power source line 1113, a sensor vertical peripheraldriving circuit 1009, a sensor horizontal peripheral driving circuit1008, and a fixed potential line 1115.

Moreover, similarly to the embodiment 1 or 2, the feature of thisembodiment is that the wiring line of the liquid crystal display elementand the wiring line of the sensor element is independent of each other.The liquid crystal display element is made up of a liquid crystal 1002,a pixel TFT 1003, a capacitance 1114, a fixed: potential line 1004, agate line connected to a display gate driver 1011, a display signaldriver 1010, and a display input signal line 1006.

While an upper electrode of a general active type image sensor is formedof a transparent electrode, the image sensor of this embodiment isdifferent from the general image sensor in that a lower electrodethereof is formed of a transparent electrode.

With respect to the operation method of the image sensor of thisembodiment, when a picture of one frame is detected, a reset pulsesignal is inputted from the reset line 1012, and the reset transistor T₁with a gate connected to the reset line is turned on. Then the potentialof an upper electrode of :a photodiode and an amplification transistoris reset to a power source potential. When the reset transistor T₁ is inan off state, the gate electrode of the amplification transistor T₂ isput in a floating state. In this state, light incident on the photodiode PD 1001 is converted into an electric charge and is stored. Bythis electric charge, the potential of the upper electrode of thephotodiode is slightly changed from the power source potential. Thechange of this potential is detected as a potential variation of thegate electrode of the amplification transistor T₂, and a drain currentof the amplification transistor T₂ is amplified. When a selection pulsesignal is inputted from a selection line 1116 is inputted, the selectiontransistor T₃ is turned on, and an electric current amplified by theamplification transistor T₂ is outputted as a picture signal to a signalline 1007.

Embodiment 4

In this embodiment, an example of a device provided with anintegral-type liquid crystal display panel having an image sensorfunction as described in the embodiments 1 to 3 will be described.

Here, a digital still camera as shown in FIGS. 11A and 11B will bedescribed. FIGS. 11A and 11B show cases in which angles of viewing aredifferent from each other by 180 degrees.

The structure shown in FIGS. 11A and 11B includes a main body 1101, adisplay portion 1106, a light receiving portion 1102 which is disposedon the back surface of the main body and in which an image sensor isdisposed, an operation switch 1105, a shutter 1104, and a stroboscopiclamp 1103.

An image sensed by the image sensor of the light receiving portion 1102is subjected to signal processing, and a still picture or a movingpicture is displayed in realtime or is taken in a memory.

Moreover, here, a portable telephone having a sensor function as shownin FIGS. 11C and 11D will be described. FIGS. 11C and 11D show cases inwhich viewing angles are different from each other by 180 degrees.

The structure shown in FIGS. 11C and 11D includes a main body 1111, adisplay portion 1117, a light receiving portion 1112 which is disposedon the back surface of the main body and in which an image sensor isdisposed, and an operation switch.

An image sensed by the image sensor of the light receiving portion 1112is subjected to signal processing, and a still picture or a movingpicture is displayed by the display portion 1117 in realtime. Alsopicture data are received from a communicating partner and aredisplayed. Further, such a structure may be adopted that picture datasensed by the image sensor of the light receiving portion 1112 are takenin the memory and are transmitted to a communicating partner.

The manufacturing process of the present invention is the same as thatof a conventional display device other than the manufacturing steps ofthe photoelectric conversion element. Thus, since a conventionalmanufacturing process can be used, the device can be, easily andinexpensively manufactured. Further, even if a sensor function isincluded, the shape and size of the substrate of the device manufacturedby the present invention are not changed from a conventional panel.Thus, the size of the device can be made small and the weight thereofcan be made light.

Moreover, since a light receiving area of a sensor cell is substantiallythe same as a pixel area of a display cell, and is large as comparedwith a single crystal CCD, the sensor of the present invention can bemade supersensitive. Further, electric power consumed in this structureis small, and electric power consumed in the image sensor can also bemade small as compared with a CCD structure.

1. (canceled)
 2. A semiconductor device comprising: a substrate; aphotoelectric conversion element comprising a first electrode, aphotosensitive semiconductor film formed over the first electrode and asecond electrode formed over the photosensitive semiconductor film; areset transistor; an amplification transistor wherein a gate of theamplification transistor is electrically connected to the photoelectricconversion element; a selection-transistor wherein an electric currentof the amplification transistor is output to an output line through atleast the selection transistor; a power source line electricallyconnected to the photoelectric conversion element and a gate of theamplification transistor through the reset transistor; a reset lineelectrically connected to a gate of the reset transistor; and aninterlayer insulating film formed over the reset transistor, theamplification transistor and the selection transistor.
 3. Thesemiconductor device according to claim 2 wherein said interlayerinsulating film comprises silicon oxide.
 4. The semiconductor deviceaccording to claim 2 wherein said interlayer insulating film comprisessilicon nitride.
 5. The semiconductor device according to claim 2wherein said interlayer insulating film comprises silicon nitride oxide.6. The semiconductor device according to claim 2 wherein saidphotoelectric conversion element is formed on said interlayer insulatingfilm.
 7. The semiconductor device according to claim 2 wherein each ofthe reset transistor, the amplification transistor and the selectiontransistor comprises a polycrystal silicon film at least as a channelformation region thereof.
 8. The semiconductor device according to claim2 wherein said photosensitive semiconductor film comprises amorphoussilicon.
 9. A semiconductor device comprising: a substrate; aphotoelectric conversion element comprising a first electrode, aphotosensitive semiconductor film formed over the first electrode and asecond electrode formed over the photosensitive semiconductor film; areset transistor; an amplification transistor wherein a gate of theamplification transistor is electrically connected to the photoelectricconversion element; a selection transistor wherein an electric currentof the amplification transistor is output to an output line through atleast the selection transistor; a power source line electricallyconnected to the photoelectric conversion element and a gate of theamplification transistor through the reset transistor; a reset lineelectrically connected to a gate of the reset transistor; and a firstinterlayer insulating film formed over the reset transistor, theamplification transistor and the selection transistor wherein saidphotoelectric conversion element is formed on said interlayer insulatingfilm; a second interlayer insulating film formed over said photoelectricconversion element.
 10. The semiconductor device according to claim 9wherein each of the reset transistor, the amplification transistor andthe selection transistor comprises a polycrystal silicon film at leastas a channel formation region thereof.
 11. The semiconductor deviceaccording to claim 9 wherein said photosensitive semiconductor filmcomprises amorphous silicon.
 12. The semiconductor device according toclaim 9 wherein said interlayer insulating film comprises silicon oxide.13. The semiconductor device according to claim 9 wherein saidinterlayer insulating film comprises silicon nitride.
 14. Thesemiconductor device according to claim 9 wherein said interlayerinsulating film comprises silicon nitride oxide.
 15. A semiconductordevice comprising: a substrate; a photoelectric conversion elementcomprising a first electrode, a photosensitive semiconductor film formedover the first electrode and a second electrode formed over thephotosensitive semiconductor film; a reset transistor; an amplificationtransistor wherein a gate of the amplification transistor iselectrically connected to the photoelectric conversion element; aselection transistor wherein an electric current of the amplificationtransistor is output to an output line through at least the selectiontransistor; a power source line electrically connected to thephotoelectric conversion element and a gate of the amplificationtransistor through the reset transistor; a reset line electricallyconnected to a gate of the reset transistor; a first interlayerinsulating film formed over the reset transistor, the amplificationtransistor and the selection transistor wherein the photoelectricconversion element is formed over the first interlayer insulating film;a second interlayer insulating film formed over the photoelectricconversion element; and a pixel electrode formed over the secondinterlayer insulating film.
 16. The semiconductor device according toclaim 15 wherein each of the reset transistor, the amplificationtransistor and the selection transistor comprises a polycrystal siliconfilm at least as a channel formation region thereof.
 17. Thesemiconductor device according to claim 15 wherein said photosensitivesemiconductor film comprises amorphous silicon.
 18. The semiconductordevice according to claim 15 wherein said second interlayer insulatingfilm comprises a resin.
 19. The semiconductor device according to claim15 wherein said interlayer insulating film comprises silicon oxide. 20.The semiconductor device according to claim 15 wherein said interlayerinsulating film comprises silicon nitride.
 21. The semiconductor deviceaccording to claim 15 wherein said interlayer insulating film comprisessilicon nitride oxide.
 22. The semiconductor device according to claim 2wherein the gate of the amplification transistor is directly connectedto the photoelectric conversion element.
 23. The semiconductor deviceaccording to claim 9 wherein the gate of the amplification transistor isdirectly connected to the photoelectric conversion element.
 24. Thesemiconductor device according to claim 15 wherein the gate of theamplification transistor is directly connected to the photoelectricconversion element.